Particulate matter in air is often undesirable (e.g., irritating to breathe, or interferes with the performance of equipment). Therefore, there is a need to remove some or all of the particulate matter from air and gas streams over extended periods of time. For example, HVAC (heating, ventilation and air conditioning) air, aircraft cabin ventilation, clean room ventilation, air to engines for motorized vehicles, or to power generation equipment, gas streams directed to gas turbines, and air streams to various combustion furnaces often include particulate material that needs to be constantly filtered or otherwise removed.
To remove particulate matter from air, filters comprising filter media and a filter frame are installed in HVAC and other systems. Efficiency is the propensity of filter media to trap, rather than pass, particulates and is generally selected to trap particles of certain sizes with certain efficiencies. For the filter media to remove particles, it is necessary for the air stream to move through the filter media (i.e., to move from the upstream to the downstream side of the filter media). In some installations, however, there may be leaks or other passageways by which the air stream can move past an installed filter without passing through the filter media. For example, there may be a hole in the filter media, a leak in the filter frame, or a leak between the filter frame and the HVAC duct into which the filter is installed. Gasketing material may be used to help reduce leakage, particularly between the filter frame and the HVAC duct. Air that moves past an installed filter without passing through the filter media will generally not have particulate matter removed from it, and thus there is a need to minimize leaks in order to achieve the intended performance, for example, the intended efficiency of particle removal of a filter in an HVAC or other system.
There is a continuing need for additional filter designs that provide desired or improved filtering efficiencies in a cost-effective manner.